Separators are widely used in hydrocarbon production and designed to separate production fluids into their constituent components of oil, gas and/or water. They work basically from the principle that the three components are of different densities which results in a stratification with gas in a top region, oil in a middle region and water in a bottom region of a separator container or tank, if the fluids are slowly passed through the separator.
The present invention is useful especially in hydrocarbon production on oil fields where there is a low gas content in the production fluids, or as part of a separation system applied in production of well fluids that normally contain no gas. In use, the present invention effects purging of gas if gas appears due to for instance out of specified operation or transients and/or due to that the system pressure is reduced. Such situation can swiftly arise in an only liquid (non-compressible) system in result of, e.g., a trapped and isolated volume being cooled down, leading to reduction in pressure and temperature followed by a gas flashing situation.
The object is to avoid free gas in the fluid that passes a liquid pump which is used to feed the production fluids, such as well fluids to a host facility. The free gas will otherwise reduce the pump performance, i.e. its ability to deliver differential pressure. Free gas may accumulate in the separator and need to be removed. A conventional gas outlet with direct flow line, such as a riser, to a host facility will not be functional in this case, based on two concerns: firstly, and because of the flow rate, the gas will be cooled down in the gas riser which may result in formation of hydrates in the gas riser, and secondly because of liquid build-up in the gas riser due to low flow velocity which may cause a liquid plug in the gas riser.